The effect of social balance on social fragmentation

Nations and communities typically function as relatively coherent groups, yet also occasionally fall apart or fragment into highly polarised sub-groups. Sociologists have puzzled over the phenomenon for more than a century, and the matter holds urgent relevance today as many modern societies around the world suffer from social fragmentation and political destabilization. Potential contributing causes include globalisation, migration and the advent of modern communication technologies, especially social media, which has created “echo chambers” in political discourse. Societies have polarised into warring tribes of like-minded individuals who filter out any information not confirming their own views. The specific scenario by which such abrupt fragmentation has come about remains unknown.
In a new paper, LML External Fellow Imre Kondor and colleagues Tuan Minh Pham, Rudolf Hanel and Stefan Thurner explore how subtle changes to interpersonal social interactions might contribute to such a transition from coherence to fragmentation. They study a model of social organization centred on the sociologist Fritz Haider’s concept of structural balance, based on the insight that triangle relations among groups of three individuals play a key role in social reality. Empirically, balanced triangles – of three mutual friends or two friends with the same enemy – tend to persist more than unbalanced triangles made of any other combination. When unbalanced triangles arise, people tend to eliminate the resulting tension by changing some links to restore balance.
From within this perspective, Kondor and colleagues studied how the emergent social reality of a group arises from the individual actions of the people making it up, as individuals try to balance their own local social conditions as best they can. Importantly, they note, peoples’ low-level decisions can be affected by global changes such as new communication technologies. In their simple co-evolutionary model, individuals try to manage social stress among their social connections by either adjusting their opinions, or by changing their social links to others from cooperative to hostile, or vice versa. In this way, the nature of society gradually changes through low-level individual adjustment. In a series of simulations based on a Hamiltonian formalism adopted from physics, the researchers find that the natural evolution leads to an abrupt regime shift or phase transition happening at critical values of social connectivity – the average number of social bonds each individual has. Below the critical density, the society remains largely cohesive, with opinions randomly distributed among individuals, and an even mix of balanced and unbalanced triangles. Above the threshold, however, strongly balanced social networks emerge and the society splinters into many small uniformly collaborative communities, these having largely hostile links towards other groups.
Significantly, as the authors note, empirical studies have found that societies historically have inhabited the cohesive region, but in the vicinity of the threshold. This puts these societies at risk of falling into the non-cohesive, polarised region through a small increase in social connectivity, something which has clearly happened in recent decades through immigration, globalisation, technology for electronic communications of many kinds and other factors. The authors hope this model may help clarify the possible origin of today’s social fragmentation, and suggest some paths forward in returning to more cohesive societies.
The paper is available at

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